1. Field of the Invention
The present invention relates to improvedly water-insensitive phosphomagnesia cements and compositions for the formulation thereof.
2. Description of the Prior Art
One of the major applications for the phosphomagnesia cements is in the rapid repair of roads, highways, bridges and airport runways. They are used to fill cracks or holes, or to cover degraded or worn areas. Other than adhering well to Portland cement, these phosphomagnesia cements have a high modulus of rupture and crush resistance, which translates that they are particularly suitable for such applications. In addition, the setting time for these cements can be as low as a few tens of minutes. Thus, once the route or roadway has been repaired, it can be reopened to traffic in a matter of a few hours after treatment.
The problem, however, is that the phosphomagnesia cements are sensitive to water. Their mechanical properties deteriorate when immersed, or simply when contacted with water.
One solution to this problem is to treat the external face surfaces of the cement with a waterproofing compound.
However, even though the aforesaid properties are improved, this type of treatment is not completely satisfactory in that it is not permanent. Indeed, whatever the application of the cement, in particular those indicated above, they are always subject to a greater or lesser degree of wear which causes the coating to disappear more or less rapidly. The cement surface must then be again treated if acceptable mechanical properties are to be retained.
It is thus apparent that this type of solution is not satisfactory as regards the final properties of the cement, nor as regards cost, since the treatment must be repeated at regular intervals.